Motors (electric motors) and dynamos (generators) have widely been used as rotary devices that convert electric energy into rotational energy or vice versa. The rotary device includes a sliding member having a slide-contact face that contacts a rotating object. The sliding member takes a form of a brush or a commutator.
For example, the motor has a brush that is always in slide contact with a commutator to make a current flow into a coil. Resistance loss and slide contact (friction) between the brush and the commutator raise the temperature of the brush and the commutator. Therefore, the life of the motor largely depends on durability of the brush. Patent Documents 1 to 6 disclose highly durable brushes.
Patent Document 1 discloses a brush formed of a resin-based material including silver powder and carbon powder mixed with a thermosetting resin. Patent Document 2 discloses a brush formed of a resin-based material including carbon powder mixed with a thermoplastic resin. Patent Document 3 discloses a brush formed of a resin-based material including copper powder, carbon powder, and zinc compound mixed with a thermoplastic resin.
Patent Document 4 discloses a non-resin-based brush formed of a sintered compact composed of silicon carbide. Patent Document 5 discloses a non-resin-based brush formed of a sintered compact composed of copper and carbon. Patent Document 6 discloses a non-resin-based brush formed of a sintered compact composed of carbon.
Patent Document 1: Japanese Patent Application Laid-Open No. 2004-124224
Patent Document 2: Japanese Patent Application Laid-Open No. 2005-229687
Patent Document 3: Japanese Patent Application Laid-Open No. 2007-28841
Patent Document 4: Japanese Patent Application Laid-Open No. 2001-37163
Patent Document 5: Japanese Patent Application Laid-Open No. 2001-119903
Patent Document 6: Japanese Patent Application Laid-Open No. 2006-67702